DSM - Piezoelectric Positioning Systems - DSM - #19

In an effort to combine the benefits of fast macro motion and precise micropositioning, DSM has developed a novel drive technology combining the features of a stepper motor linear actuator and a piezoelectric actuator (PZT) that share a common displacement feedback device. With the high speed and force of a stepper motor linear actuator and the very fine motion of a piezoelectric actuator, the SPIN drive can satisfy many of today's demanding micropositioning applications.

A prototype version of the drive assembly is pictured at right. It uses a standard stepper motor linear actuator and a 25 pm stroke PZT actuator. The glass scale encoder features a resolution of down to 5 nm. DSM is happy to consider custom configurations and integration into larger platforms.

Target commercial applications include microscopy and the manufacture of multi-axis alignment systems for precision assembly processes in photonics, electronics packaging, and MEMS.

• Combined macro and micro motion with 5 nm resolution (also available without the encoder or with coarser resolutions)

• 15+ mm stroke (application dependent)

• Output force up to 30 lb. (speed dependent)

• Output speed up to 20 mm/s (load dependent)

• Fast (300 Hz) 5 micron dither on top of macro motion

• 5 nm open loop minimum step size

• Total macro stroke:

Determined by length of stepper motor screw, length of glass scale, and length of crossed roller guide.

• Motion resolution:

5 nm resolution provided by MicroE Systems Mercury 3500 series encoder. The encoder bridges both the stepper motor linear actuator and the PZT actuator and is located near the drive's output.

• Dimensions:

Standard size 17 stepper motor with 20 mm PZT stack (scaleable for larger/smaller systems)

• Supporting electronics:

Stepper driver control is offered with "smart motor" configurability using the IMS stepper driver chip and RS232 field bus connectivity in a compact package with greatly reduced wiring requirements. DSM's linear piezo amplifier provides power and control to the PZT actuator.

The SPIN Drive technology is intended to allow fast macro motion with the stepper motor using the encoder to monitor a calculated move distance. Final "pull-in" moves are accomplished by the PZT actuator, and the PZT compensates for any backlash inherent to the stepper motor.

The design of the SPIN Drive hardware is based on solid state flexures that are stiction- and backlash-free. The flexure design ensures that the output of the PZT is purely linear in order to minimize lost motion due to compliance and rotation in the hardware frame. Since the encoder bridges both stepper and PZT actuator, any errors due to stiction/friction or windup in the stepper actuator or compliance in the PZT-Stepper coupling are eliminated.

DSM has extensive experience in actuator design for specialized force or stroke requirements. Customers are encouraged to contact DSM regarding any specific actuator requests.